This invention relates generally to workpiece conveyor systems of the type disclosed in issued U.S. Pat. No. 4,615,273 entitled "Conveyorized Transport System" and assigned to the assignee herein. A related application Ser. No. 249,442 filed concurrently herewith and entitled "Transfer Slide Assembly and System" and said issued U.S. Pat. No. 4,615,273 are incorporated by reference herein.
Workpiece conveyor system of the type with which this invention is concerned may, for example, be used in a garment making plant to carry workpieces to a series of work stations. Without such a system a garment worker, in addition to performing a particular work operation on each piece, often has to punch a label attached to each workpiece to make a record of its status, sort the workpieces, and transport them manually to and from the various work stations. These additional steps cause the typical garment worker to consume time, and create other problems in the assembly process. For example, the time it takes a worker to perform various tasks is generally unpredictable and difficult for supervisory personnel to keep track of. Also, it is difficult to keep track of the workpieces and the time required as they travel to and from various stations. In order to provide a more accurate scheduling of such work it is common for operators to accummulate many workpieces before carrying them to a subsequent work station, so considerable inventory may be tied up in a factory, introducing excessive costs to the manufacturer. Furthermore, accummulating workpieces in such piles tends to make accurately updated quality control inspections more difficult.
As disclosed in the above mentioned U.S. Pat. No. 4,615,273 a conveyorized transport system is provided having a main rail upon which trolleys ride, and having closed subsidiary loops located alongside the main rail, each such loop leading to and from an individual work station. Switching means is provided for each such loop for transferring trolleys between the main rail and such subsidiary loops. These loops each have an entrance and an exit end, the entrance being upstream of the exit relative to the general direction of trolley movement on the main conveyor. This switch is able to deliver a trolley to the entrance and to receive a trolley from the exit of each loop.
This loop configuration provides flexibility in routing because it allows trolleys to be routed in two or more ways from the exit of a subsidiary loop. In accordance with one feature of the above mentioned patent a trolley switches between the main rail and a subsidiary loop and is positively propelled by a series of spaced pushers so that the switching is reliable and consistent. The main rail and subsidiary loop each have a gap and the switch comprises a rail section that can be moved during switching from a first position bridging in the gap in the main rail to a second position bridging the gap in the subsidiary loop to provide for transfer of the trolley from the main rail to the subsidiary loop. This type of switch also allows the trolley to be routed from one subsidiary loop to another located directly across the main rail, or vice versa, or from the discharge end of the subsidiary loop directly to the entrance of the same subsidiary loop for recirculation purposes.
As further described in said prior art patent each closed subsidiary loop includes an inclined gravity rail portion for feeding the trolleys to and through a work station, and includes an elevator means for lifting the trolleys from the lower end of the gravity rail assembly to a point and to a level where the trolleys can be reloaded on the main conveyor track.
The primary aim of the present invention is to provide an improved gravity rail assembly for the subsidiary loop or loops of a conveyorized transport system of the type shown and described in U.S. Pat. No. 4,615,273.